Xanthophylls are oxygenated carotenoid compounds occurring in green vegetation (e.g., corn, marigolds, and the like) and in some animal products (most notably egg yolks). The xanthophylls are yellow pigments which can be used in both animal and human foods and in pharmaceuticals. The xanthophylls in natural feed sources are used often to provide natural pigmentation for poultry (especially chickens) and their eggs. Examples of such natural feed sources include yellow corn, corn gluten meal, marigold meal, and algal meal. Such xanthophyll-containing materials impart the desirable healthy yellow color or hue to broiler chickens when included in chicken feed.
Use of natural feed sources to provide xanthophylls can lead to inconsistent results, mainly observable in the variation of color levels obtained in broiler chickens. In many cases, such natural feed sources can differ greatly in the bioavailability of the xanthophylls, the xanthophyll content, and xanthophyll stability. These problems often result in poor correlation between the chemical analysis of the feed material (i.e., amount of xanthophylls present) and the biological performance (i.e., color development in the broiler).
Attempts have been made to extract xanthophylls from vegetable matter such as corn and marigold meals. For example, Soviet Patent Application 1,819,619 provides a method for the extraction of flavonoids and carotenoids from marigold petals. The petals are ground and then extracted seven times with ethanol at 70.degree. C. for 40 minutes per extraction. After distilling off the alcohol, the extract is dissolved in castor oil. This material generally contains about 30 weight percent flavonoids (e.g., patuletin, patuletrin, quercetagetin, quercetagetrin, and quercetin) and about 15 weight percent carotenoids (e.g., xanthophyll, rubsanthin, helenien, carotene, and violazanthine) from the original marigold petals. This material was used for medicinal purposes. Most commercial xanthophylls in used today are derived from marigold petals and are, as a result, relatively expensive.
More recently, Cook et al., U.S. Pat. No. 5,254,673 (Oct. 19, 1993), provided a method for treating corn gluten meal to purify corn zein. Pigments, including xanthophylls, were generated as by-products. Wet or gently dried corn gluten was subjected to a combination of enzymatic starch hydrolysis, alkaline treatment, alcohol washing, followed by either alcohol extraction or fractionation of the deflavored and decolored gluten. Pigments were reported to be recovered in the alcohol washing step which consisted of washing in "a continuous counter-current fashion or by batch-wise washing with fresh alcohol at each step." No details were given in regard to the amounts or quality of the recovered by-product pigments.
We have now duplicated the Cook et al. method using corn gluten (containing about 12 weight percent moisture). Xanthophylls recovered by the method described by Cook et al. generally have a rubber-like or paste-like consistency. In contrast, the xanthophylls recovered by the method of the present invention are a crystalline, powdered material with a stronger yellow color. Moreover, xanthophylls are recovered by the Cook et al. method in significantly lower yields and at significantly lower efficiencies as compared to the recovery method of the present invention. Xanthophylls recovered by the Cook et al. method must undergo significant further purification (with decreasing yields) to obtain xanthophylls which can be used in food products. The xanthophylls produced by the method of this invention are suitable for use in food products with significantly less further purification.
It would be desirable to recover xanthophylls from a natural source such as corn gluten in high yields and efficiencies. It would desirable to obtain xanthophylls as a crystalline powder from a natural source such as corn gluten. It would also be desirable to obtain xanthophylls from a natural source such as corn gluten in a purity suitable for use in food products. The method of the present invention provides such xanthophylls.